Whole-body kinematics and coordination in a complex dance sequence: Differences across skill levels

Body Posture and Low Back Pain: Differences between Folk and Ballroom Dancers

(1) Background: Dance is extremely diverse in its styles. Each of them presents different training, dynamics, and figures that may impact the body posture and the occurrence of low back pain. This observational study aimed to compare the sagittal curvatures and the range of motion (ROM) of the spine, as well as the low back pain occurrence and its intensity between folk and ballroom dancers. (2) Methods: Fifty-one participants took part in the study (nineteen folk dancers, fifteen ballroom dancers, and seventeen non-dancers) aged 18-32. Study groups did not differ in anthropometric parameters as well as in dancing experience and training frequency. Study procedures included a self-administered questionnaire and a physical examination of the sagittal spine curvatures and ROM. The questionnaire included questions about epidemiological data and the occurrence of chronic pain and its intensity using a Visual Analogue Scale (VAS). (3) Results: There was a significant difference in thoracic kyphosis angle between study groups (p = 0.02). The greatest angle was found in folk dancers and the lowest in ballroom dancers (40 vs. 33 respectively). We have found no significant differences in spine ROM, low back pain occurrence, and intensity between study groups (p > 0.05). We have found no correlation between low back pain and spine curvatures and ROM in dancers (p > 0.05), however, we found a very strong and negative correlation between thoracic spine range of motion and the pain intensity in non-dancers (R= -0.95, p = 0.003). The analysis also revealed that only in folk dancers, but not in ballroom dancers, the BMI correlates positively with dancing experience (R = 0.67, p = 0.002). (4) Conclusions: There are no differences in low back pain occurrence and pain intensity between folk and ballroom dancers, however, the prevalence of low back pain in dancers is very high. Folk dancers seem to have more flexed body posture compared to ballroom dancers.

A primitive-based representation of dance: modulations by experience and perceptual validity

The generation of complex movements such as dance might be possible due to the utilization of movement building blocks, i.e., movement primitives. However, it is largely unexplored how the temporal structure of a movement sequence and the recruitment of these primitives change with experience. Therefore, we obtained a representation of primitives with the temporal movement primitive model from the motion capture data of dancers with varying experiences, both for improvised and choreographed movements (elements from contemporary/modern/jazz) with different qualitative expressions. We analyzed differences between movement conditions regarding the number of temporal segments and the number of primitives, as well as their association with dance experience. Especially for the choreography with a neutral expression, the results indicate a negative association between experience and the number of segments and a positive association between experience and the number of primitives. The variation in the recruitment of these primitives suggests an increased consistency of modular control with experience, particularly for improvised dance. A prerequisite for the meaningful interpretation of these results regarding human movement production is that the model can generate perceptually valid dance movements. This was confirmed in a subsequent experiment, although the validity was slightly impaired for improvised movements. Overall, the results of the choreographed movement sequences suggest that experience is associated with an increase in motor repertoire that might facilitate fewer and longer temporal segments.NEW & NOTEWORTHY This study demonstrates that a temporal movement primitive model, trained with movements performed by dancers with different levels of experience, is able to generate natural-looking dance movements. The results suggest that motor experience in dance is associated not only with fewer temporal segments but also with an increase in the number of underlying movement building blocks. The recruitment of these primitives, which might be used to simplify movement production, additionally seems to become more consistent with experience.

How partnering changes the process of postural control?

The aim of the study was to identify changes in the mechanism of postural control among ballroom dancers between standing solo and standing with a partner during specific standard dance positions. Specifically, the study attempted to determine whether the male partner plays a stabilising role in the dance couple. A total of seven competitive dance couples participated in the study. The experimental procedure comprised four dance positions characteristic of international standard dances: standard, starting, chasse and contra check. The dance positions were staged twice - while standing solo and while standing with a partner. The assumption of the assessed position was preceded by a dance phase after which the participants were instructed to freeze on a force plate and hold the position for 30 s. To examine whether subjects standing solo or with partners had greater rambling (RM) or trembling (TR) components in their dance postural profile, the ratios of RM to the center of foot pressure (COP) and TR to COP were computed for velocity. No significant differences were observed in the velocity of COP between standing solo and standing with a partner (p > 0.05). However, during the standard and starting positions, female and male dancers standing solo were characterised by higher values of the velocity of RM/COP ratio and lower values of the velocity of TR/COP ratio than those standing with a partner (p < 0.05). According to the theory behind the RM and TR decomposition, an increase in TR components could indicate a higher reliance on spinal reflexes, which would suggest greater automaticity.

Postural and Gestural Synchronization, Sequential Imitation, and Mirroring Predict Perceived Coupling of Dancing Dyads

Body movement is a primary nonverbal communication channel in humans. Coordinated social behaviors, such as dancing together, encourage multifarious rhythmic and interpersonally coupled movements from which observers can extract socially and contextually relevant information. The investigation of relations between visual social perception and kinematic motor coupling is important for social cognition. Perceived coupling of dyads spontaneously dancing to pop music has been shown to be highly driven by the degree of frontal orientation between dancers. The perceptual salience of other aspects, including postural congruence, movement frequencies, time-delayed relations, and horizontal mirroring remains, however, uncertain. In a motion capture study, 90 participant dyads moved freely to 16 musical excerpts from eight musical genres, while their movements were recorded using optical motion capture. A total from 128 recordings from 8 dyads maximally facing each other were selected to generate silent 8-s animations. Three kinematic features describing simultaneous and sequential full body coupling were extracted from the dyads. In an online experiment, the animations were presented to 432 observers, who were asked to rate perceived similarity and interaction between dancers. We found dyadic kinematic coupling estimates to be higher than those obtained from surrogate estimates, providing evidence for a social dimension of entrainment in dance. Further, we observed links between perceived similarity and coupling of both slower simultaneous horizontal gestures and posture bounding volumes. Perceived interaction, on the other hand, was more related to coupling of faster simultaneous gestures and to sequential coupling. Also, dyads who were perceived as more coupled tended to mirror their pair's movements.

High intra-task and low inter-task correlations of motor skills in humans creates an individualized behavioural pattern

Our motor system allows us to generate an enormous breadth of voluntary actions, but it remains unclear whether and how much motor skill translates across tasks. For example, if an individual is good at gross motor control, are they also good at fine motor control? Previous research about the generalization across motor skills has been equivocal. Here, we compare human performance across five different motor skills. High correlation between task measures would suggest a certain level of underlying sensorimotor ability that dictates performance across all task types. Low correlation would suggest specificity in abilities across tasks. Performance on a reaching task, an object-hitting task, a bimanual coordination task, a rapid motion task and a target tracking task, was examined twice in a cohort of 25 healthy individuals. Across the cohort, we found relatively high correlations for different spatial and temporal parameters within a given task (16-53% of possible parameter pairs were significantly correlated, with significant r values ranging from 0.53 to 0.97) but relatively low correlations across different tasks (2.7-4.4% of possible parameter pairs were significantly correlated, with significant r values ranging from 0.53-0.71). We performed a cluster analysis across all individuals using 76 performance measures across all tasks for the two repeat testing sessions and demonstrated that repeat tests were commonly grouped together (16 of 25 pairs were grouped next to each other). These results highlight that individuals have different abilities across motor tasks, and that these patterns are consistent across time points.

Applications of Biomechanical Foot Models to Evaluate Dance Movements Using Three-Dimensional Motion Capture: A Review of the Literature

Dance movement requires excessive, repetitive range of motion (ROM) at the foot-ankle complex, possibly contributing to the high rate of injury among dancers. However, we know little about foot biomechanics during dance movements. Researchers are using three-dimensional (3D) motion capture systems to study the in vivo kinematics of joint segments more frequently in dance-medicine research, warranting a literature review and quality assessment evaluation. The purpose of this literature review was to identify and evaluate studies that used 3D motion capture to analyze in vivo biomechanics of the foot and ankle for a cohort of dancers during dance-specific movement. Three databases (PubMed, Ovid MEDLINE, CINAHL) were accessed along with hand searches of dance-specific journals to identify relevant articles through March 2020. Using specific selection criteria, 25 studies were identified. Fifteen studies used single-segment biomechanical foot models originally created to study gait, four used a novel two-segment model, and six utilized a multi-seg- ment foot model. Nine of the studies referenced common and frequently published gait marker sets and four used a dance-specific biomechanical model with purposefully designed foot segments to analyze the dancers' foot and ankle. Description of the biomechanical models varied, reducing the reproducibility of the models and protocols. Investigators concluded that there is little evidence that the extreme total, segmental, and inter-segmental foot and ankle ROM exerted by dancers are being evaluated during dance-specific movements using 3D motion capture. Findings suggest that 3D motion capture is a robust measurement tool that has the capability to assist researchers in evaluating the in vivo, inter-segmental motion of the foot and ankle to potentially discover many of the remaining significant factors predisposing dancers to injury. The literature review synthesis is presented with recommendations for consideration when evaluating results from studies that utilized a 3D biomechanical foot model to evaluate dance-specific movement.

Static Balancing Ability and Lower Body Kinematics Examination of Hungarian Folk Dancers: A Pilot Study Investigating the “Kalocsai Mars” Dance Sequence

Folk dance is a collection of traditional dances that requires years of practicing to perform correctly. The aim of the present study was to develop a complex biomechanical measurement procedure that investigated Hungarian folk dancers’ balancing ability and lower body kinematics through a dance movement called “Kalocsai mars”. Therefore, 11 dancers’ motion (5 female and 6 male; age: 20.5 ± 2.5 years; height: 173.82 ± 7.82 cm; weight: 64.77 ± 8.67 kg) was recorded with an optical-based motion capture system and force platforms simultaneously. Before and after the dancing session, static balancing tests were performed, examining bipedal stance with eyes opened and closed conditions. The ANOVA results showed that the values of the range of motions of the knee joint flexion-extension angles and hip flexion averaged for sessions increased significantly (p=0.044, p=0.003, p=0.005) during the dancing sessions. The deviation in the joint angle was greater in the nondominant legs, suggesting that the nondominant side requires more attention to execute the dance steps correctly. The results of the balance tests showed that the oscillation in the posterior direction increased significantly after dancing (p=0.023). In comparison, the visual feedback had no significant effect on the dancers’ balancing ability.

Analysis of Whole-Body Coordination Patterning in Successful and Faulty Spikes Using Self-Organising Map-Based Cluster Analysis: A Secondary Analysis

This study investigated the whole-body coordination patterning in successful and faulty spikes using self-organising map-based cluster analysis. Ten young, elite volleyball players (aged 15.5 ± 0.7 years) performed 60 volleyball spikes in a real-game environment. Adopting the cluster analysis, based on a self-organising map, whole-body coordination patterning was explored between successful and faulty spikes of individual players. The self-organising maps (SOMs) portrayed whole body, lower and upper limb coordination dissimilarities during the jump phase and the ball impact phases between the successful and faulty spikes. The cluster analysis illustrated that the whole body, upper limb and lower limb coordination patterning of each individual’s successful spikes were similar to their faulty spikes. Range of motion patterning also demonstrated no differences in kinematics between spike outcomes. Further, the upper limb angular velocity patterning of the players’ successful/faulty spikes were similar. The SPM analysis portrayed significant differences between the normalized upper limb angular velocities from 35% to 45% and from 76% to 100% of the spike movement. Although the lower limb angular velocities are vital for achieving higher jumps in volleyball spikes, the results of this study portrayed that the upper limb angular velocities distinguish the differences between successful and faulty spikes among the attackers. This confirms the fact that volleyball coaches should shift their focus toward the upper limb velocity and coordination training for higher success rates in spiking for volleyball attackers.

Directional Dependence of Experimental Trunk Stiffness: Role of Muscle-Stiffness Variation of Nonneural Origin

Trunk stiffness is an important parameter for trunk stability analysis and needs to be evaluated accurately. Discrepancies regarding the dependence of trunk stiffness on the direction of movement in the sagittal plane suggest inherent sources of error that require explanation. In contrast to the common assumption that the muscle stiffness remains constant prior to the induction of a reflex during position perturbations, it is postulated that muscle-stiffness changes of nonneural origin occur and alter the experimental trunk stiffness, causing it to depend on the sagittal direction. This is confirmed through reinterpretation of existing test data for a healthy subject, numerical simulation, and sensitivity analysis using a biomechanical model. The trunk stiffness is determined through a static approach (in forward and backward directions) and compared with the model stiffness for assumed scenarios involving deactivated muscles. The difference in stiffness between the opposite directions reaches 17.5% without a preload and decreases when a moderate vertical preload is applied. The increased muscle activation induced by preloads or electrical stimuli explains the apparent discrepancies observed in previous studies. The experimental stiffness invariably remains between low and high model-stiffness estimates based on extreme scenarios of the postulated losses of muscle activation, thereby confirming our hypothesis.

Timing is everything: Dance aesthetics depend on the complexity of movement kinematics

What constitutes a beautiful action? Research into dance aesthetics has largely focussed on subjective features like familiarity with the observed movement, but has rarely studied objective features like speed or acceleration. We manipulated the kinematic complexity of observed actions by creating dance sequences that varied in movement timing, but not in movement trajectory. Dance-naïve participants rated the dance videos on speed, effort, reproducibility, and enjoyment. Using linear mixed-effects modeling, we show that faster, more predictable movement sequences with varied velocity profiles are judged to be more effortful, less reproducible, and more aesthetically pleasing than slower sequences with more uniform velocity profiles. Accordingly, dance aesthetics depend not only on which movements are being performed but on how movements are executed and linked into sequences. The aesthetics of movement timing may apply across culturally-specific dance styles and predict both preference for and perceived difficulty of dance, consistent with information theory and effort heuristic accounts of aesthetic appreciation.